Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F29/00—Variable transformers or inductances not covered by group H01F21/00
  • H01F29/02—Variable transformers or inductances not covered by group H01F21/00 with tappings on coil or winding; with provision for rearrangement or interconnection of windings
  • H01F29/04—Variable transformers or inductances not covered by group H01F21/00 with tappings on coil or winding; with provision for rearrangement or interconnection of windings having provision for tap-changing without interrupting the load current
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
  • H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
  • H02M5/02—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc
  • H02M5/04—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters
  • H02M5/10—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using transformers
  • H02M5/12—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using transformers for conversion of voltage or current amplitude only

Definitions

• the invention relates to the electrical distribution and in particular the adjustments to the transformation ratios in order to keep the circulating voltage within acceptable limits despite possible load fluctuations.
• the invention relates to a medium voltage (LV) / low voltage (LV) transformer apparatus in which the main transformer is associated with a device for modifying the transformation ratio without requiring the transformer to be switched off. main.
• the electrical networks are generally structured in several levels separated by transformer substations: after a first very high and high voltage distribution and transmission network, a medium voltage MV or MV distribution network, usually between 1 and 35 kV, and more precisely 15 or 20 kV in France, allows smaller-scale transport, to customers of industrial type or LV low-voltage networks (in particular 0.4 kV in France) that supply customers with low energy demand.
• MV / LV distribution transformers are thus designed with a ratio between the input and output voltage, or transformation ratio, determined to ensure a voltage level compatible with user-side standards.
• the conventional mechanical solution achieves the change of transformation ratio by modifying the number of turns on the primary side (MT), by separating the primary winding into a main part and an adaptable part.
• MT primary side
• the switches of the adaptable part are placed in oil that is polluted during the electric arcs generated. by the passage from one outlet to another.
• vacuum bulbs see WO 2012/062408, which however increase the cost and bulk of the initial transformer.
• Another option to overcome the problems of mechanical switching presented for example in FR 2 873 489 or WO 2010/072623, comprises the use of semiconductors for the passage from one outlet to another.
• the invention aims to overcome the drawbacks of existing adjustment devices, and in particular to provide a reliable and inexpensive system of selection of suitable outlets for MV / LV oil transformers.
• the invention thus relates to a voltage transformation apparatus comprising a first main transformer, the ratio of which is determined by the desired MV and secondary primary circuit voltages BT.
• it is an oil transformer.
• the apparatus is provided with means for adjusting the main transformation ratio off load, prior to the connection of the electrical device to the network and according to the characteristics of said network.
• the apparatus further comprises a second adjustment transformer, preferably also oil and located in the same vessel as the main transformer, the secondary winding of which is connected in series with the primary circuit of the main transformer.
• the primary winding of the adjustment transformer comprises at least two plugs, in particular at the ends, and preferably three.
• the transformation ratio of the adjustment transformer is advantageously chosen to correspond to a predetermined percentage N, typically between 0.5% and 5, in particular 2.5, of that of the main transformer when it is connected to the main transformer by the main transformer. one of the end plugs; if a third central tap is provided, it is desired that it be in the center of the primary winding, to generate an adjustment transformation ratio equal to twice the agreed adjustment value, in particular to 5, of the ratio of main transformation.
• At least two outlets, preferably the end taps, of the adjustment transformer are associated with three connection lines: a first connection line to the secondary circuit of the main transformer provided with first switching means, a second connection line. to another phase or the neutral of the secondary circuit provided second switching means, and a third connecting line, or "bypass" line, to the secondary circuit of the main transformer provided with third switching means and a load impedance.
• the two bypass lines share their load impedance.
• the other plugs of the adjustment transformer may comprise only one connection line provided with switching means to the secondary circuit of the main transformer.
• the switching means operate in the air, and are preferably grouped together on a single board accessible directly for an operator.
• the transformation apparatus also comprises a control system of the switching means of the outlets, which can be integral with the apparatus or be deported, and preferably supplied via the secondary circuit of the main transformer.
• the apparatus according to the invention is provided with means making it possible to ensure that at least one of the connection lines of two different sockets is closed, so that the transformer primary adjustment is not open circuit.
• a safety circuit in particular provided with switches similar to the switching means, is placed between the first and second lines of each socket; alternatively, the switching means may be chosen to be in a bistable position and / or associated with position-keeping devices.
• an installation according to the invention comprises three devices as previously defined, the transformers of which are preferably housed within the same oil tank and whose switching means are also preferably housed on the same plate.
• the three devices of the three-phase electrical installation are advantageously of identical characteristics and parameters, and in particular the three transformers, main and / or of adjustment, can themselves be composed of unit blocks covering the three phases.
• the control system is able to control the switching means of the different taps simultaneously, and preferably, the switching means are electromechanical contactors operating in the air, which can be associated with position-keeping devices.
• Figure 1 shows a three-phase electrical installation according to a preferred embodiment of the invention.
• FIG. 2 represents the electrical diagram of an installation according to the invention.
• Figures 3A to 3F illustrate adjustment steps in an apparatus according to the invention.
• a three-phase electrical installation 1 can take up the elements and conventional characteristics of a commercial three-phase transformer assembly, as illustrated in FIG. 1.
• the electrical installation 1 advantageously comprises a vane with fins 3 filled with oil or other dielectric fluid in which are housed the transformation elements themselves, and from which emerge through and other connecting devices 5 on the MV network and to the cabinet 7 and the LV network.
• main processing element it is possible to use a main transformer block housed in the tank 3, for example adapted for 630 kVA, with a primary circuit at 20 kV - 18.2 A and a secondary circuit at 410 V - 887 A, or three identical 10-phase transformers, or any other system.
• means are provided for adjusting and adjusting on site the transformation ratio (s) of the main transformation element, before starting, depending on the local conditions MT / BT of use, the location of the installation 1 ..., for example a conventional off-load tap changer.
• the invention uses an adjustment transformer unit, in particular with a second adjustment transformer 20 associated with each main transformer 10.
• the second adjustment transformer 20 size smaller than the main transformer 10 but which may be of the same nature, can be implemented in the same oil tank 3.
• the second adjustment transformer 20 is provided with sockets that allow its association or not with the main transformer 10.
• the invention does not use the principle of the transformer "booster" (according to conventional English terminology) as a voltage transformer, but as a current transformer.
• a simple booster transformer as presented in CN 20158428 does not solve the problem of implementation complexity if the tap change is made in oil by complex devices or semiconductors.
• the invention is based on the use of a proven tap-switching system 30, with switching on the low voltage devices themselves located in the air and not immersed in the tank 3: thus, the Oil tank 3 is not polluted and the production parameters are easy to implement, since they are submerged transformers 10, 20 known for a very long time.
• the maintenance is easy, the switching elements 30 can be directly accessible from the outside.
• a second transformer 20 is associated with the main transformer 10, said second transformer 20 taking the voltage of the secondary circuit, treating it, and injecting it in series on the primary voltage to adjust it.
• This adjustment of the primary voltage MT automatically causes a change in the LV voltage.
• the switching means 30 only see the current flowing in the adjustment transformer 20 and not in the complete network.
• the switching means 30 are then electromechanical contactors marketed and commonly used for example for the control of motors, the cost is reduced and the predictable performance, which further offer the advantage of grouping in the same device the switching means of the three phases.
• the primary windings of the main transformer block and secondary of the adjustment transformer block are put in series on the MV network, the secondary winding of each transformer main 10 corresponding to the phases of the LV network.
• the primary windings of the transformer transformer unit comprise several plugs 22, 24, 26 which may or may not be connected to the corresponding winding of the main transformer block on the LV network.
• the plug 22, 24, 26 the current flows in all or part of the primary winding of the adjustment transformer 20, and the transformation ratio of the assembly 10, 20 housed in the tank 3 is modified, thus modifying the voltage of the secondary network BT (assuming that the voltage MT is imposed by the generator 6).
• connection lines provided with switching means are implemented.
• each socket 22, 24, 26 of each phase U, V, W is connected by a line provided with a first switch 32 2 , 32 4 , 32 6 on the corresponding U, V, W phase of the LV network.
• a first switch 32 2 , 32 4 , 32 6 on the corresponding U, V, W phase of the LV network.
• two plugs at least 22, 24 are connected by a line provided with a second switch 34, on another phase V, U, W of the LV network.
• a connection on the neutral could also be provided. In the preferred embodiment illustrated, only the two end plugs of the winding 22, 24 are connected to said second connection line, which proves to be sufficient and reduces the number of necessary contactors.
• the adjustment transformer is used as a current transformer, while the tap change can be performed under load. It must therefore be ensured that the passage of the current is never interrupted in the adjustment transformers 20, otherwise there will be an overvoltage in their windings and breakage of elements of the installation 1.
• Means to ensure that the closing of at least one of the contactors of two different plugs 22, 24 are therefore provided, in this case, in the illustrated embodiment, by the presence of contactors on a safety circuit 38 which is automatically closed in case of default. Any other option is conceivable, for example the use of switching means other than industrial contactors designed to be normally open to meet the safety standards of motor starts.
• the contactor plate 30 is associated with a control system 40 of the switching means.
• the control system is fed directly to the LV network via suitable means.
• the control system 40 can be placed on the oil tank 3, or it can be put in place in a remote cabinet, for example for off-site control via wired connection.
• the control system 40 is designed to allow switching from one tap to the other in a predefined contact closure / opening sequence depending on the degree of adjustment of the required transformation ratio.
• the adjustment principle will be illustrated in connection with FIG. 3 for a single-phase apparatus and the passage of a zero adjustment, i.e. only the main transformer 10 is used, at an adjustment of + N% and + 2-N%. In the initial position (FIG.
• the three receptacles 22, 24, 26 are disconnected from the phase of the LV network, that is to say that the five contactors 32, 36 of the first and third lines are open, and only the contactors 34 of the second lines of the end jacks 22, 24 are closed; these two contactors 34 2 , 34 4 are kept mechanically closed to ensure safety during a possible loss of voltage.
• a disconnection of the adjustment plug 24 is performed by following the steps in the opposite direction, and in particular by passing through the intermediate step of closing the third contactor 36 of the load impedance Z during any switching between the first and second contactors. 32, 34.
• the solution according to the invention while using additional components whose cost and bulk are minimal in view of the constraints on the transformers related to the power of the installation 1, thus allows a setting of the nominal power with degrees variation that can be adjusted precisely on site, before commissioning, depending on the location of the transformer and the nature of the local network.
• the variations of the transformation ratio of the installation 1 are then carried out safely, particularly in the case of the use of bistable contactors, without requiring a vacuum interrupter, a power electronics, or even a voltage measurement or current.
• the adjustment of the transformation ratio is accurate, with a range that can be fine, especially 2.5 and 5%.
• the control of the transformation variations can be carried out remotely, or directly on site, by means of a standard PLC designed to operate in a constraining industrial environment, and in particular without voltage and / or current measurement.
• the maintenance is equivalent to that of existing transformers, the contactors being themselves proven, reliable and easily accessible solutions.
• the invention has been described with reference to a 630 kVA three-phase MT / LV oil distribution transformer assembly driven by industrial type contactors, it is not limited thereto: other transformers and other switching means may be concerned by the invention.
• the primary circuit of the adjustment block 20 can be connected in series with the primary windings of the transformer block 10, the secondary of the adjustment block 20 being controlled with a phase and the neutral.
• the electromechanical contactors it is possible to use semiconductor or other type of switching means.
• the entire range of MV / LV transformers can be affected by the adjustment according to the invention, in particular from 100 to 2500 kVA, for an MT network of 5 to 36 kV and a LV network of 220 to 440 V .

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Housings And Mounting Of Transformers (AREA)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

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• 2013
  • 2013-04-08 FR FR1353112A patent/FR3004284B1/fr active Active
• 2014
  • 2014-03-27 EP EP14719047.4A patent/EP2984663B1/de active Active
  • 2014-03-27 ES ES14719047.4T patent/ES2636645T3/es active Active
  • 2014-03-27 AU AU2014252950A patent/AU2014252950B2/en active Active
  • 2014-03-27 WO PCT/FR2014/050719 patent/WO2014167205A1/fr active Application Filing
  • 2014-03-27 CN CN201480022284.2A patent/CN105164769B/zh active Active

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